The invention concerns a drill for applying seed and fertilizer having a frame, reservoirs, sowing shares with at least two separate inlets for seed and fertilizer and a depth adjustment or pressure roller mounted behind each share and wherein the materials to be applied are conveyed in controller amounts to the shares for application into the soil and the shares are connected to the frame with parallelogrammatic mounts and the depth to which they penetrate into the soil can be adjusted by means of an setting device.
A drill of this type is known from German OS No. 2 552 810. The advantage of this drill is that it has depth-adjustment or pressure rollers mounted behind the sowing shares that make it possible to precisely adjust the depth of each share so that each share can apply the materials at a uniform depth even over the most uneven ground. The seed and fertilizer are always applied at a previously determined depth.
This drill has a drawback, however, in that the seed and fertilizer must always be applied together. It is tremendously important, especially in the zero-tillage method, to be able to apply seed and fertilizer separately. When they are applied together, the two materials come into contact and the fertilizer can, especially if it has a high percentage of nitrogen, at least to some extent corrode the seed. The result is significant overrun damage and decreased yield.
Another drawback to this drill is the shape of the sowing share, which generates very large lateral soil displacement. This is especially disadvantageous in zero tillage, which depends on displacing as little soil as possible. The known share also breaks up the soil to a large extent, resulting in the loss of a lot of the moisture in the soil, so that the germinating and growth conditions awaiting the seed are very poor. The shapes of these shares are also not very appropriate for use on rocky soils because the rocks damage and dull them very rapidly.